The Climate in Emergency

A weekly blog on science, news, and ideas related to climate change

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Considering Packaging

I think packaging is bad. Buying products in bulk using reusable containers (cloth or glass, ideally) is much better. Recyclable packaging is better than non-recyclable, but not as good as no packaging at all, and not really OK. When I can’t avoid buying a package, I feel guilty. When my husband doesn’t avoid buying a package, I feel angry.

I’m not unusual in any of this. Plenty of environmentalists think and feel as I do.

But are we right?

Questioning Packaging

I don’t doubt that packaging carries an environmental cost. Most things do, after all, and many resource conservation efforts are organizing around reducing packaging, packaging waste, and litter (much of which is discarded packaging). I don’t doubt the rightness of such efforts.

But consider proportion and context.

Too many environmentalist life-style changes are the equivalent of picking up pennies from the sidewalk—sure, go ahead and do it, but don’t expect much from the exercise. Yes, pennies add up to dollars and dollars add up to wealth, but anybody who expects to earn a living by picking up dropped pennies is deluding themselves. Anyone who expects to save the planet one teeny-tiny bit at a time is similarly delusional. Some things just aren’t worth irritating one’s husband over—other things very much are.

In which category does packaging fall?

To ask about the importance of packaging, though, it’s necessary to rephrase the question. For one thing, “packaging” is not just one thing but a whole flock of products made of differing materials, for differing reasons, and by differing production methods. It took me a whole extra week to figure out how to ask my question so as to be able to find an answer—the key is to look at the substance, not the product at all.

What are the carbon footprints and environmental impacts of small amounts (a pound, say) of the various materials commonly used in packaging? How do these footprints compare with other aspects of a household carbon footprint, such as burning a gallon of gas?

About Plastics

Plastics are a group of substances. I discussed them in a previous post, and the important thing to remember is that what is true of one plastic is not necessarily true of another. Some are a recyclable, some are not. Most cannot biodegrade, but some can, at least under very specific circumstances. Most plastics are made from petroleum, but some are not. Perhaps surprisingly, whether a plastic is made from plants has nothing to do with whether it’s biodegradable; what matters is the chemistry of the product, and the same polymers can be assembled from multiple kinds of oil.

I have not attempted to look up the environmental impact of every single kind of plastic there is, nor have I tried to look up all the kinds regularly used in packaging. Instead, I used search terms such as “the carbon footprint of plastic,” and came up with a few specifics and some generalities that should be roughly applicable to most, if not all plastics.

The important thing to remember is plastics generate questions that have no simple answers. More on that shortly.

The Carbon Footprint of Plastics

According to one study, in 2015 the greenhouse gas emissions from all plastics worldwide, from cradle to grave and including transportation, was almost 1.8 billion metric tons of carbon dioxide equivalent. Not all of that plastic is packaging, and while it’s a good guess that much of it is, I’m not really sure. The article didn’t say. The article also didn’t put that number in perspective–is 1.8 billion a big chunk of total emissions, or a small one? You’d think it would be easy, in the information age, to just look up humanity’s carbon footprint for a given year, especially since it’s easy to find out how much emissions grow or shrink from year to year, or how the footprint of one country compares to that of another. But nope, that information is buried somewhere.

It’s another example of the societal innumeracy I was talking about last week.

But the authors of the article seemed to think 1.8 billion is cause for concern and that plastics are an area that deserves specific attention in the fight against climate change.

Another source looks at plastic bottles and helpfully explains the following:

The manufacture of one pound of PET (polyethylene terephthalate) plastic can produce up to three pounds of carbon dioxide. Processing plastic resins and transporting plastic bottles contribute to a bottle’s carbon footprint in a major way. Estimates show that one 500-milliliter plastic bottle of water has a total carbon footprint equal to 82.8 grams of carbon dioxide.

Again, that’s hard to put in perspective, but since a gallon of gasoline burned produces 20 pounds of carbon dioxide, and one gram is 0.00220462 of a pound, it seems about 109 plastic bottles equal one gallon of gas, footprint-wise. 109 bottles is about a two-week supply for someone who drinks mostly bottled water or soda.

So, yeah, if you drive to the store for a load of groceries, the carbon footprint of your drive will likely be higher than the footprint of the plastic packaging, but it might be close. And if you bike to go shopping in order to reduce your emissions, as I do, cutting back on plastic packaging seems a quite reasonable next step.


There is always a but, and the but of avoiding plastic is that the alternative is sometimes worse. It’s hard to be sure, first because the analysis has to include many factors, and in part because sources of information often have their own motives.

For example, the Coca-Cola Bottling Company (which sells both plastic and glass bottles as well as aluminum cans) reports that glass bottles have been gaining market share against plastic lately, but cautions that glass is not always superior environmentally. Their argument is that it takes less energy to make a plastic bottle than a glass one, and that as long as both are recycled, the problem of plastic in the environment is irrelevant. We’ll get back to the issue of recycling, but Coca-Cola’s analysis may be correct as far as it goes. And if it does take less energy to make a plastic bottle, it probably takes less money, too–so the company has a financial incentive to reposition plastic as a low-carbon option, whether or not it is one.

Financial incentive is not proof of nefariousness, but it’s reason to be suspicious. It’s reason to ask how the carbon footprint of plastic compares to glass after manufacture, in transportation and disposal and so forth–notice the article didn’t say.

But, But….

But there is food for thought out there. For example, plastic packaging on vegetables–which I’ve always viewed as pointless–turns out to increase the shelf-life of such vegetables and thus increase the chance that they will sell. Food waste has a huge carbon footprint, and while vegetables spoiling on grocer’s shelves represent only a fraction of that waste, the thin film of plastic on a cucumber is only a very tiny amount of packaging. I lean towards rejecting the plastic wrap anyway, but without the certainty I used to have.

Then, too, plastic is much lighter than glass, lighter than aluminum, and often slightly lighter than cardboard, meaning that plastic packaging requires less energy to transport than packaging made from its competitors does. Less energy means lower carbon footprint. Again, certainty lessens.

And there are other applications where plastic definitely has a much lower footprint than its alternatives, and customer resistance to plastic is actually a barrier to a company lowering its footprint. As ever, knee-jerk reactions prove counter-productive. There is no alternative to learning and thinking.

But, But, But….

Carbon emissions are not the only form of environmental impact around, and plastic pollution is now a major problem. All other packaging materials, if dropped in the ocean, either biodegrade or eventually turn into sand of one kind or another. Only plastic stays plastic forever.

In some cases, it might be necessary to pick one’s poison.

Cardboard and Paper

Corrugated cardboard has a footprint in carbon dioxide equivalent about equal to half it’s own weight. That is, if you’re looking at a pound of cardboard, you’re also looking at half a pound of carbon dioxide equivalent. So, 40 pounds of cardboard equals a gallon of gas–given that you need a lot of cardboard to get 40 pounds, we’re getting into penny-territory here, something that matters a lot in aggregate but not so much otherwise.

There are other kinds of cardboard and other paper products used in packaging, and except for those laminated with plastic or foil, most are likely similarly low-carbon.

It’s worth noting that most cardboard packaging is removed before products hit the shelves; almost everything–including items sold in bulk, naked on shelves–arrives at stores in big cardboard boxes. I’ve worked in grocery stores, and breaking down boxes for disposal is a common activity. Hopefully, they are recycled. I was never quite clear on whether ours were–they did go into a different compactor from the rest of the store’s trash. But the point is that there is a lot more cardboard associated with your groceries than you can see. But because consumers have no direct contact with this cardboard, it doesn’t fall under the heading of consumer lifestyle choice. If reducing cardboard use is a worthy goal (and it might not be, since complications abound), we need to lean on suppliers to meet that goal, rather than attempting to meet it ourselves.


According to one source, glass that has not been recycled has a carbon footprint 8.4 times its own weight. Recycled glass has a footprint 1.4 times its own weight. So how much of the glass we buy is recycled and how much is not? I don’t know–it’s most likely a mix.

A glass bottle weighs, on average, eight ounces, so two bottles per pound. I don’t know how big an average glass bottle is, but let’s say that you’re buying both beer and wine in variously-sized glass bottles, and so your personal average bottle weight happens to also land on eight ounces per. So if you buy 28 bottles, you’ll have about 14 pounds of bottle glass. If those bottles are made from all-recycled glass, that’s 20 pounds of associated carbon dioxide equivalent, the same amount you’d get from burning that gallon of gas.

If those bottles are made entirely of never-recycled glass, you’ve got 117.6 pounds of carbon dioxide equivalent on your hands.

Like I said, it’s probably a mix.


Metal, in packaging, is almost exclusively aluminum nowadays. I spent the better part of an hour fighting with figures provided by one source on aluminum before I discovered the document’s decimal points had gone screwy–a good example of why looking up this type of information can be tricky (another reason is that different assessments may go by different rules and turn up numbers that shouldn’t be compared). On a different source, I found recycled aluminum listed as having a carbon footprint twice its own weight (one pound of aluminum represents two pounds of carbon dioxide equivalent) and unrecycled aluminum listed as having a footprint 12 times its own weight.The big difference reflects the fact that mining and processing aluminum ore (bauxite) requires a huge amount of energy–bauxite mining is reportedly terrible in other respects, too.

In practice, aluminum products like cans are likely a mix of recycled and new metal. Since I don’t know what the mix is, I don’t know what the footprint  of an aluminum can or an aluminum foil wrapper might be. If the mix is 50/50 (as implied but not stated by the source with the screwy decimals which I’m not going to site) the footprint should be seven times the weight of the metal. That’s a start.

So, if one pound of aluminum corresponds to seven pounds of carbon dioxide equivalent, how many aluminum cans make up a pound? Answer: 31 cans. Sometimes information is easy to find, for a change.

That means roughly 93 aluminum cans, or 15 six-packs and three singles, have a carbon footprint equal to burning a gallon of gas if my guess about the recycled content is right.

So, What Do I Buy?

I did find one source that list various types of drinks container in order from best to worse for the environment. The same source also lists carbon footprints for each, but you’ll notice I’ve done this post the hard way by looking up each material in a different source–believe it or not that wasn’t an oversight. I wanted to be able to see if discrepancies emerged between the various sources. It was a form of quick-and-dirty fact-check, and that is how I noticed there was a problem with the source with the wacky decimal places.

I can’t directly check my numbers against this last helpful source, though, partly because it lists carbon footprints per bottle whereas my numbers are by the pound, and partly because it gives low, medium, and high estimates and they diverge wildly (the high estimate for single-use plastic is over ten times the low estimate). This raises the question–are my numbers the result of high, low, or medium estimates?

This last article does a good job of covering both carbon footprints under various scenarios and other environmental impacts, such as pollution. I recommend reading it.

An important take-away is that the environmental impact of various types of packaging depends in part on where you live because recycling options, reuse options, and the energy grid itself all vary. That’s why I’m not reproducing their best-to-worst list (sorry); every entry except “no container” has the caveat, “depending on country.”

So, Does Packaging Matter?

Short answer? Yes, but probably not as much as I thought it did.

In general, for a large shopping trip with most items packaged in something or other, packaging may add the equivalent of a gallon or so of gas to the trip. That’s not nothing, but it’s likely a relatively small part of the household footprint.

Which type of packaging is better is a difficult call, especially since plastic has a low footprint but a terrible environmental impact for other reasons (plastic is almost never closed-loop recycled, either; recycled plastic still ends up in a landfill or the ocean, it just takes a detour through being a carpet or something on the way). There are other complications, too. For example, glass seems like a great option because it can be sterilized and reused, but it almost never is. Individual companies can vary a lot, too. For example, the Cliff Bar company is carbon neutral and is a leader in sustainable industry, so while its wrappers clutter up our house and drive my husband to distraction (I forget to throw them out), they might not count towards our footprint the same way an apparently similar wrapper from a less-enlightened company would.

Practically speaking, there are two choices for a household wishing to reduce its packaging-related footprint: research each product and its packaging individually; or consider all packaging to be roughly equivalent and minimize its total weight.

The latter approach, while definitely quick and dirty, should lead to impact reduction in most cases and has the advantage of being doable.


  1. First, reduce total weight of packaging so far as can be done without making yourself crazy or alienating your spouse.
  2. Where possible, choose recyclable options over those that are not recyclable.
  3. Where possible, choose glass over even recyclable plastic.
  4. Where possible, support environmentally and socially responsible companies, not those that aren’t.

And don’t forget to vote for climate hawks, because that’s really where we’re going to win this thing, not in arguments over cracker boxes.



Hot Little Number

A lot of people—perhaps most—are functionally innumerate.

Innumeracy sounds like it ought to be the mathematical equivalent of illiteracy, and it is something like that, and yet it is also different. And yes, this has to do with climate change.

Illiteracy is primarily a problem of knowledge—an illiterate person doesn’t know enough about the written language to understand it. It’s possible to be innumerate in that sense, and that kind of numeracy can lag far behind literacy for some. For example, I am so fully literate that I make my living as a writer and an editor, and yet I don’t actually know how big a million is. I could count to ten thousand, if I wanted to, but I couldn’t count to a million. I don’t know how.

But there is another form of innumeracy that has less to do with knowledge and more to do with the ability to use mathematical logic. For example, if I say “300 people died of food poisoning this year,” that doesn’t tell you anything. Am I talking about an outbreak in a small town, or am I talking about the entire United States? How many people die of food poisoning in a typical year—is 300 more or fewer than usual? Only with context does this number, 300, tell a meaningful story.

Knowing where to look for that context and how to interpret that context is the beginning of statistical literacy, a related but different issue, but if you don’t know some kind of context is necessary, then you might as well not know the number 300, either.

That’s functional innumeracy.

The reason this matters for climate change is that again and again in the course of researching for this blog I find numbers presented to the public without their context, or with inadequate context.

  • Product A. requires more energy to produce than Product B.–does that include manufacture only, or does it also include the energy required for acquiring raw materials?
  • A certain university boasts that it has reduced its carbon emissions by a certain number of tons per year—but what is the new carbon footprint, and is it bigger or smaller than typical for similar schools?
  • Nationally, a certain substance is responsible for a certain number of tons of carbon dioxide equivalent—but is that number big or small compared to the footprint of the country as a whole?

I realize it’s a little difficult to make sense of hypothetical examples, but I’m trying to keep this post quick and to the point, without getting bogged down with real-life detail.

When I see numbers presented without context, I wonder whether the people presenting those numbers don’t realize the context is necessary, or if they simply aren’t as interested in climate action as they appear to be? Indeed, careful attention to which context is missing often reveals something that could be to the advantage of the entity releasing the numbers—but whether the oversight was actually deliberate, I’m not in a position to say.

I can confidently assert, though, that the fact context is not given means that the public doesn’t demand it. And that means there are important questions, questions that could make a great deal of difference to how we attack climate change, that we’re not asking. It also means that we’re leaving ourselves vulnerable to people who sound good but don’t have the facts on their side.

Innumeracy is unlike illiteracy in that the latter can really only be fixed by education. You can’t will yourself to read if you don’t know how. But if you understand numbers in a general way—and most of us do—you can will yourself to think more carefully about them, and on the basis of careful thought you can ask more questions.

Sometimes that’s all that needs to happen, to begin with—ask a couple of good questions.

And then seek answers.

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Roofs for Heaven

So, our roof sprung a leak.

I realize some might question my sharing this small bit of personal woe, but really, what homeowners don’t have an issue now any then? In fact, I’m told that roofs need to be replaced routinely–it’s an expected hassle, especially for some of the shorter-lived roof types. That means you, too, might be in the market for a new roof, and if you’re not now, (if you’re lucky enough to own a home) you will be someday in the future.

So what kind of a roof do we want?

The thing is that roof-shopping is an opportunity, a chance to make decisions about some small corner of the built environment instead of simply accepting it as a given. What sort of roof do I want? Can I have one that’s different? That’s especially mine? That better suits my tastes and values and generally makes me happy to live beneath?

Can, in other words, a roof be a response to the challenge and crisis of climate change?

Yes, it can.

Roof-Related Issues

First, let’s take a look at how roofs are related to climate change. In my reading, I’ve identified three broad categories of relevance: roofs have carbon footprints, so it’s possible to choose a roofing type with a small one; roofs have an impact on the energy use of the house; and some roofs have additional tricks, such as generating renewable electricity.

All of these together, plus such practical matters as cost, become part of the picture for making a final choice.

The Roof’s Footprint

Roofs, like everything else, have a carbon footprint. One way for a homeowner to respond to the climate crisis is to get a roof with a smaller footprint. I was able to find a study that did compare the carbon footprints of various roofing types, at least in Australia, but unfortunately it did not include asphalt shingle, which is the simplest and least-expensive in our area.

The study compared typical residential roofs of sheet metal, clay tile, and concrete tile, including in each case the wooden frame beneath (though not, apparently, insulation). The analysis looked at both greenhouse emissions and embodied energy for each from cradle to grave and found out that the footprint of metal roofing can differ radically depending on whether it is recycled afterwards. The abstract of the paper (reading the full text would require money I don’t have) did not include all of the relevant numbers, so I had to do some math. “CO2e-” means carbon dioxide equivalent, recognizing that there are other greenhouse gasses and their warming potential varies. CO2e- is a way to quantify and express warming potential as a single figure regardless of which greenhouse gasses in what relative quantities are involved.

It’s also not clear from the abstract how much of each roofing material was involved–obviously, larger roofs would have bigger numbers–but the roof in the analysis was the same size in each case. “T” presumably stands for metric tonne, which is somewhat larger than the American ton.

  • Clay tile has a carbon footprint of 4.4 t of CO2e-.
  • Sheet-metal roofing that is not recycled has a carbon footprint of 9.85 t of CO2e-.
  • The carbon footprint of concrete tile wasn’t given, but is intermediate.
  • Sheet metal roofing that is recycled “can obtain significant carbon and embodied energy saving benefits (i.e. 71–73%) compared to clay tile or concrete roof covers,” a grammatically ambiguous statement that seems to suggest the following:
    • Metal roofs, if recycled, have a carbon footprint of 1.27 t of CO2e-
    • Concrete tile has a carbon footprint of 4.7 t CO2e-


  • Metal, if later recycled = 1.27
  • Clay = 4.4
  • Concrete = 4.7
  • Metal, if not later recycled, = 9.85

Curiously, concrete tile, not never-recycled metal, has the highest embodied energy.

So, what about other materials? Unfortunately, figures from different analyses aren’t directly comparable, since analyzing carbon footprints requires making a lot of arbitrary decisions about what to include and what not to include–and each person who does such an analysis ends up making those decisions differently. So I can’t combine results from multiple studies. Anyway, I wasn’t able to find life-cycle analyses of other roofing materials.

I did find an American analysis of the carbon footprints of disposing of various construction materials, including asphalt shingles, and the article did comment on the footprint of construction. Curiously, shingles made with a core of fiberglass felt have a lower footprint than those made of more natural-seeming paper felt, since paper absorbs water and must be dried, a process that takes energy. The fiberglass variety are already far more common.

Another surprise was that incinerating the shingles lowers the footprint of disposal because they can replace other fuels for energy generation, including fuels that have more greenhouse gas emission for the same amount of energy–shingles can’t be incinerated in most facilities because of “impurities” (I’m guessing this means air-quality concerns?) but are accepted as fuel for cement kilns in Europe. Asphalt shingles can also be melted down and added to the asphalt mixes used in roadways, which reduces the total amount of asphalt used and thus lowers emissions related to sourcing the material. Asphalt shingles can, in theory, be recycled into new asphalt shingles, but it’s technically difficult and nobody is doing it. The shingles can’t be composted. None of that is very useful for a homeowner, though, especially as I don’t have access to a European cement kiln.

And I wasn’t able to compare the footprint of asphalt shingles to that of metal roofing.

The Roof’s Role in the House’s Footprint

What type of roof a house has can alter the energy use (and thus the carbon footprint) of the house as a whole. For example, a white roof reflects heat and keeps the house cooler, reducing the temptation to use the air conditioner. A black roof absorbs heat and keeps the house warmer, reducing the need for heating in winter. Which one is better depends on the local climate where the house sits and whether the occupants tolerate cold or heat better. There may, in the future, be coatings available that will darken or lighten in response to temperature, but as yet we must pick a color.

Different materials also vary in their ability to conduct heat into the house, so asphalt shingles will warm a house more than a metal roof of the same color–both because asphalt absorbs a lot of heat and because asphalt roofs are designed to transfer as much heat as possible from the shingles to the house beneath, since otherwise the shingles get too hot and are damaged by heat.

A roof with excellent insulating capacity will keep the house temperature from varying as much, an advantage in both hot and cold weather. The R-value (insulating ability) of a whole roof typically depends largely on a layer of insulation, because the roofing surface tends to have a low R-value no matter what it’s made of, but they do vary, so a material with a higher R-value is better, all else being equal. Asphalt shingle is .44 and wooden shingle is .97. I wasn’t able to get a figure for metal roofing, but it is similar to that of asphalt.

Roofs with Benefits

There are roofs that do more than simply cover the top of the house.

Green roofs, that is roofs designed to support living plants, reduce local air pollution, reduce storm-water run-off, provide animal habitat (depending on what’s planted up there), and can even grow food (if the roof is accessible enough to harvest). They also sequester carbon, although the chance of that carbon remaining sequestered very long is slim–most have to be replaced after about 40 years.

Solar roofs incorporate solar panels and generate electricity.

And, while it’s a bit off-topic for us here, flat roofs surfaced in gravel provide nesting habitat for certain birds (nighthawks, for example).

Roofing Materials

It’s no good just asking what roofing material is “better for the climate” in a vague way. To make a decision, we have to know what kinds of benefits we’re talking about. Now, we do know, so we can get on with exploring specific materials.

Asphalt Shingle

Asphalt shingles are made out of sheets of felt (either paper-based or, more commonly, fiberglass) that have been soaked in a thick type of asphalt and sprinkled with coarse sand. They are popular because they are cheap and, in the short term, sturdy (though quality can vary a lot). Unfortunately, their R-value is low, they conduct a lot of heat into the house, and they don’t last very long. Most must be replaced about every 20 years, meaning that however large their carbon footprint is, a sixty-year-old house roofed in asphalt has three such footprints, not one.


Metal roofs are moderate in cost (higher than asphalt but lower than some other options) and relatively long-lasting, on the order of 60 years. Their R-value is low, but they conduct very little heat into the house, especially if given a heat-reflective coating. If the metal will be recycled at the end of their service, their total carbon footprint is quite low. They resist most kinds of damage very well, don’t burn (important, as climate change makes wildfires more frequent!), and don’t support the growth of moss or algae, though they can be dented by hail. Many different styles are available–metal roofs can be made to look like several other materials–but do have one aesthetic disadvantage; rain falling on them is very noisy.

Wood Shingles

Wooden shingles are carbon neutral, or close to it (processing and transportation surely involve some emissions), can be made with reclaimed wood from other buildings, and unlike almost all other options, they can be composted upon retirement. The price is only a little higher than asphalt shingle. While at first consideration they seem excellent, I have noticed that even buildings with wood shingle siding almost never have wood shingle roofs. I’m not sure I’ve ever seen a wood shingle roof, come to think of it. Why not?

Wood shingle is actually not recommended from an environmental perspective, at least not by people who don’t sell wood shingle. The problem is two-fold. First, while they can last 30 years under good conditions, wood shingles are vulnerable to rot, and many don’t last even as long as asphalt shingles do–that makes them less economical and increases their environmental impact. Perhaps more importantly, they are relatively dark in color, so they absorb heat. I assume they could be painted, but at the cost of much of their aesthetic value. They are also less fire-resistant than most other roofing types.

Green Roofs

Green roofs have all the advantages of a garden, plus they’re great at keeping the house cool. Unfortunately, the weight of the soil and water means that not all buildings can support these roofs. Installation is also expensive, though not necessarily more so than higher-end forms of traditional roofing.

Green roof designs are categorized by soil depth (and therefore what kinds of plants can grow on them) and by how much maintenance, including irrigation, they need. The categories are labeled “intensive,” “semi-intensive,” and “extensive.” It is possible to have a roof that is only partially covered by a garden and is otherwise more traditional.

Solar Roofs

Solar roofs involve tiles that are each little solar panels. I’m not sure what their virtues as roofing are, and they are more expensive that traditional solar panels; their primary advantage is that they don’t look like solar panels. It’s a moot point for my husband and I anyway, as we live in a forest.

Passive solar energy, in which water is heated in the roof, might also count as a “solar roof,” but is again rendered moot for us by trees.

Other Roofs

There are other roofing options, such as slate, rubber (made to look like slate), concrete tiles, clay tiles, and good-old-fashioned thatch. I love the idea of thatch, and I’ve heard it performs very well. If gathered locally, its carbon footprint could be virtually zero. However, dry thatch likes to catch on fire, and the chance of our finding a qualified thatcher in Maryland is just about nil. The other options are either expensive or hard to find or both, and also easily damaged by hail or other impacts (perhaps not the best thing as climate change makes extreme weather more likely).

That being said, slate has a very low carbon footprint and is reputed to be environmentally excellent, according to multiple sources, most of which sell slate. Clay and concrete have moderate carbon footprints, as already noted. I have not found figures for the other “others.”

The View From (or of) the Roof

Since it doesn’t look like I can have thatch or a green roof, I’ll be pushing for metal. If we end up priced out of that, white-painted asphalt shingle will do, though paint doesn’t stick to shingle very well. Metal is much easier to make white, and I like the fact that it lasts much longer.

Our area has hot summers and cool, but not cold, winters. We are also prone to wind–in the decade or so I’ve been here, we’ve had to cope with hurricanes, nor’easters, a derecho, a tornado, and frequent blustery days (it’s too windy to bike for several days in any typical week). We therefore need a roof that resists wind, rain, and stuff falling on the roof (such as tree branches) and that can keep our house as cool as possible in the summer. We do not need help keeping the house warm in the winter, especially since we heat with sustainably harvested wood, not with fossil fuel. Given our forested lot, solar shingles don’t make sense, especially since we buy renewably-sourced electricity anyway. And cost is a consideration because are not independently wealthy.

Your considerations, and thus your conclusions, may differ.


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Climate Change and Food: Fake Meat

A cheeseburger sitting on a wooden surface against a dark blue background. The burger is seen from the side, up-close. It's in-your-face meat. The burger has two patties, lettuce, tomato, onion, and pickle, thin slices of yellow, semi-melted cheese, and a sort-of pinkish sauce. The bun is attractively brown and shiny and has a few white seeds on its surface.

Photo by amirali mirhashemian on Unsplash

Some time ago, I wrote a post on climate change and meat. I did some reading, and learned that, yes, animal-based foods do have categorically larger carbon footprints than plant-based foods. Worse, processing and transportation have very little to do with it–eating local, organic, minimally-processed etc. may be a good idea for many reasons, but climate change is not one of those reasons. The vast majority of the carbon footprint of an edible animal is simply due to the fact that it is an animal.

I couldn’t find a detailed explanation as to why, but a likely explanation has to do with the flow of energy. Simply put, every time energy changes form, a portion of it is lost (as per the Second Law of Thermodynamics) and the higher on the food chain you eat, the more energy has been lost along the way–and the more energy is involved, the more carbon emissions (I’m summarizing the post on meat, here, which I linked to above).

Lamb and beef, in that order, are by far the worst for the climate, at least in part because both are ruminants and therefor have digestive processes that produce huge amounts of methane, a powerful greenhouse gas.

So while I’m not going to say everyone necessarily should become vegan (only the Sith deal in absolutes!), it is clear that meat cannot remain a major staple for large numbers of people.

But many of today’s vegetarians and vegans eat diets that look and taste as much like omnivorism as possible, thanks to the wonders of food science. The prevalence of fake meat and dairy is only likely to grow as the fakes get more and more appealing.

So, what’s the carbon footprint of fake meat?

Carbon Foot-printing Fake Meat

Several dishes of food sit on a wooden table. The dish nearest the camera consists of cubes of tofu in a red sauce garnished with what looks like ground black pepper and chopped green onion. The other dishes are harder to see, but may be a large bowl of white rice, a dish of sauted green beans, and a dish of sliced eggplant in a brown sauce.

Photo by Alana Harris on Unsplash

What I’m calling “fake meat” here includes anything that can stand in for meat on the table but was never part of a living animal. In some cases the phrase is a misnomer. A portobello burger, for example, doesn’t resemble meat and isn’t meant to, it’s just a vegetarian dish that is good in some of the same ways hamburgers are. And ground beef made from cloned cells in a lab (which can be done, it’s just too expensive to market yet) is real meat by any reasonable definition, it just wasn’t taken from a dead animal. But “fake meat” is a reasonable shorthand for the entire dietary genre.

Clearly, with such a wide variety of possible foods, we’re not after just one carbon footprint. On the other hand, tracking down individual footprints for anything that could possibly be used as a meat substitute would be time consuming and, in some cases, fruitless (I have tried; there is a reason I’m posting one day late this week!).

What we’re really after is a generality; is shifting to fake meat really a good idea for the climate? The short answer is a very cautious yes.

Making the Sausage

Fake meat, by definition, isn’t what it looks like or tastes like, so the trick is to pay attention to what it is, not what it seems to be.

A meatless hot dog made of seitan, for example, has much more in common with a hot dog bun than a hot dog, from either a nutritional or environmental perspective. Seitan is essentially wheat protein. It’s made by rinsing all the starch out of whole wheat dough. Carbon-footprinting a seitan product therefore involves analyzing the emissions involved in wheat production, plus those involved with processing. A meatless hot dog made of soy might have a very different footprint, and lab-grown cells would be different yet again.

One of the most exciting fake meats at the moment is the Impossible Burger, which has been through multiple iterations and is currently made mostly out of soy protein flavored with heme, a molecule found in blood that is partially responsible for the distinctive taste of red meat. It is largely thanks to heme that the Impossible Burger is almost indistinguishable in taste tests from ground beef. Fortunately, heme is not found only in blood. In this case it’s produced by genetically-engineered yeast.

Carbon-footprinting the Sausage

The Impossible Burger has been the subject of formal footprint analysis; its global warming potential (including that involved in processing) is 89% smaller than that of beef. There are a lot of details I have not been able to gather about that analysis (the footprint of beef can vary slightly, depending on how it’s raised and processed and so forth, so did they use average beef, or one particular kind for the comparison?), but I have a hard time imagining that the unknowns could make more than a few percentage points of difference either way.

Some back-of-the-envelope calculations (using figures from this article) therefore suggest that an Impossible Burger patty has a carbon footprint somewhere between that of an equivalent weight of rice and beans and an equivalent weight of egg. From a climate change perspective, it is a vegetable.

Most other processed fake meats are likely in the same range, for the simple reason that they, too, are vegetables, and processing them is unlikely to involve substantially more emissions than processing the Impossible Burger does.

Lab-grown meat could be an exception, simply because it is so different from other products–it deserves its own analysis–but since commercially viable production methods have not yet been developed, it’s too soon to say what the emissions of those methods might be.


As I wrote in my post on meat, carbon-footprinting animal products may be a little less straight-forward than it seems. For example, milk has a much smaller footprint than beef does, presumably since the footprint of the cow is spread out over her lifetime production of milk, rather than the smaller bulk of her meat alone. So the more meals an animal produces, the smaller her associated per-meal carbon footprint is? If that’s the case, then beef made from a cow previously used for milk should have a smaller per-pound footprint than dairy does, since eating the meat spreads the animal’s emissions out even farther. But is that true, or is there a piece of the puzzle missing?


More troubling yet is the issue that cattle and sheep are hardly new, so how can their emissions be causing a new problem? The obvious answer is that there are far more cattle and sheep and other domestic animals than ever before–much of the zoological part of the biosphere is currently either humans or animals being raised to be eaten by humans–but before we created what I like to call the modern massive mountain of moo, there were lots more wild animals. How can domestic animals have more emissions than the wild animals they replaced?

The reality is that climate change is best understood by looking at the biosphere as a whole, not by adding up the carbon footprints of various individual activities. Prior to the Industrial Revolution, the levels of greenhouse gasses in the atmosphere were, roughly speaking, stable, because the energy flow through the biosphere was stable, inputs balanced by outflow, like a savings account kept roughly stable through careful budgeting. Lately, though, we’ve been spending down the account, an activity that produces the short-term illusion of riches but always results in poverty at the end,

There are two forms of spending down the account: we can take energy out of long-term storage, by burning fossil fuels, or we can take energy out of short-term storage through unsustainable use of natural resources, such as excessive logging. Although there are greenhouse gasses, such as CFCs, that are a bit of a different story, the bulk of the problem of climate change is a shift in the energy flow of the biosphere caused by one form or another of spending down the account.

The question is, how can the replacement of wild ruminants by domestic cattle and sheep change the energy budget of the planet? Isn’t a bovine fart a bovine fart whether the bovine in question is a steer or a bison?

I haven’t seen this issue addressed by any other authors, but in some way or other, the way we raise meat animals must either require fossil fuels or it must constitute an unsustainable use of a living system. If meat did neither, it could not alter the energy budget of the biosphere.

A Vision for Moo

There are certainly those who believe we must all go vegan, or at least nearly vegan, for the good of the planet. The statement is controversial, in large part because there are considerations other than climate in play. Eating animals is the subject of legitimate ethical debate, an important consideration, albeit an unrelated one (it is possible for two equally important issues to have no direct bearing on each other). Eating animals is also an intrinsic part of various cultural and economic systems (another important but different issue). And there are environmental issues associated with meat other than climate–for example, grazing animals have been used in ecological restoration (for examples and discussion, please read this book and that book). So how all these various considerations might pull and tug real life into the actual future is far from clear.

But I’m still stuck on how the mountain of moo changes the biosphere.

Meat animals can’t possibly be contributing to climate change simply because they are eaten by humans as opposed to by wolves or carrion beetles. Since we have it on good authority that they are part of the problem, they must be so either because fossil fuel is used on their behalf, or because they are themselves consuming resources at an unsustainable rate.

Vegetables could also be produced with fossil fuels and at an unsustainable rate, and they eventually would be if humans all went vegan but did not otherwise change our habits.

The solution is therefore to make meat (and everything else) fossil fuel free and sustainable.

Now, there would be much less meat in such a scenario, so diets would have to change, but that would be an effect, not a cause. It’s the energy budget we have to fix first and centrally, otherwise we’re just rearranging deck chairs on the Titanic.

Does that make switching to the Impossible Burger pointless?


We won’t build a new food production system if we continue to demand food that requires the old one. We have to create the tools we’ll need to build the future, and arguably that includes fake meat that meat enthusiasts want to eat. We need to develop the production systems, the distribution systems, and the cultural preferences that the future demands, and we need to do it today.

But let’s not forget that the one thing we really must stop eating is oil.

Image appears to show the instant after a drop has dripped into a liquid; there is a crater in the liquid surface, surrounded by rings of ripples. The liquid is black with a dull, pale sheen. It could be water seen at night, or black ink, or it could possibly be black petroleum.

Photo by Julian Böck on Unsplash